Pollution and Oil Shortage

In 1966 separate legislation was enacted requiring exhaust-emission control devices on all cars built after January 1, 1968. The federal exhaust-emission control law followed the enactment of similar standards in California, where unburned hydrocarbons polluting the atmosphere over the city of Los Angeles had been a problem for many years.

The automotive industry introduced two exhaust-emission systems designed to control the emissions of the internal-combustion engines. One of the systems involves injecting air into the exhaust gas as it flows from the cylinder to the exhaust manifold. The introduction of fresh air at combustion temperatures continues the oxidation process in the exhaust system, so that more of the hydrocarbons and the carbon monoxide are burned before being emitted into the atmosphere. The other system involves engine modifications to improve carburetion, distributor calibration, and combustion, measures that effectively control exhaust emissions.

The 1970 Clean Air Act required U.S. automobile manufacturers to design more efficient and “clean” engines in order to reduce harmful emissions by 90 percent before 1976. But the deadline for meeting these standards was postponed to the 1980 model year because of the fuel crisis of the mid-1970s and technological difficulties. The government also stipulated that the average mileage for all cars be 11.7 km/liter (27.5 mi/gallons) by 1985.

Rising gasoline prices led to an increased demand for small cars, and U.S. manufacturers turned out their own models to compete with foreign ones. But the future lay in “downsizing” even standard models to reduce weight and increase economy. High-strength plastics and aluminum replaced steel in many components, and smaller, more efficient engines were designed. Chief among these were dual displacement engines, stratified charge engines, and engines aided by turbochargers. Small computers began to be used to control carburetion. Plans for volume production of electric cars were under study for the mid-1980s, but cash shortages hampered development work.

In 1994 the EPA allowed 12 states to adopt automobile emissions standards that were above the national standard and that required the automobile industry to introduce a new class of cars by 1999. The automobile industry objected to the stricter, more expensive standards but the EPA allowed the states to impose them.

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